A highly selective electrochemical sensor for trace determination and speciation of antimony (III & V) in water and soil samples using 2-thenoyltrifluoroacetone

Sensitive Silver-Enhanced Microplate Apta-Enzyme Assay of Sb3+ Ions in Drinking and Natural Waters

The toxic effects of antimony pose risks to human health. Therefore, simple analytical techniques for its widescale monitoring in water sources are in demand. In this study, a sensitive microplate apta-enzyme assay for Sb3+ detection was developed. The biotinylated aptamer A10 was hybridized with its complementary biotinylated oligonucleotide T10 and then immobilized on the surface of polysterene microplate wells. Streptavidin labeled with horseradish peroxidase (HRP) bound to the biotin of a complementary complex and transformed the 3,3',5,5'-tetramethylbenzidine substrate, generating an optical signal. Sb3+ presenting in the sample bounded to an A10 aptamer, thus releasing T10, preventing streptavidin-HRP binding and, as a result, reducing the optical signal. This effect allowed for the detection of Sb3+ with a working range from 0.09 to 2.3 µg/mL and detection limit of 42 ng/mL. It was established that the presence of Ag+ at the stage of A10/T10 complex formation promoted dehybridization of the aptamer A10 and the formation of the A10/Sb3+ complex. The working range of the Ag+-enhanced microplate apta-enzyme assay for Sb3+ was determined to be 8-135 ng/mL, with a detection limit of 1.9 ng/mL. The proposed enhanced approach demonstrated excellent selectivity against other cations/anions, and its practical applicability was confirmed through an analysis of drinking and spring water samples with recoveries of Sb3+ in the range of 109.0-126.2% and 99.6-106.1%, respectively.

A Highly Sensitive Electrochemical Sensor Based on Electrocatalytic Reduction Effect of Cu2+ on Trace Determination of Malathion in Soil and Other Complex Matrices

The current strategy reports a highly sensitive and selective square wave-cathodic stripping voltammetric protocol for malathion determination. The established method was based on the controlled adsorptive accumulation of malathion in the presence of Cu2+ ions in an aqueous solution of pH 2 onto the hanging mercury dropping electrode (HMDE) and measuring the resulting cathodic peak current of the adsorbed species at −0.42 V versus Ag/AgCl electrode. The low limits of detection (LOD) and quantification (LOQ) of malathion of the assay were estimated to be 3.1 × 10−10 and 1.03 × 10−9 M with a linear dynamic range of 1.03×10−9 – 2.0 × 10−7 M, respectively. The method was satisfactorily applied and validated for malathion determination in environmental samples. The experimental Student texp and Fexp values did not exceed the tabulated ttab (2.78) and Ftab (6.39) at 95% (P = 0.05) confidence (n = 5), confirming the precision and independence on the matrix. The developed sensing platform for the detection of malathion shows superior performance to conventional electrochemical methods. The proposed sensor offered simple, economical, reproducible, and applicable approach for the determination of malathion in environmental samples.